HRI: Hierarchic Radio Imaging-Based Device-Free Localization

Device-free localization (DFL) is a technology which helps locate the target without the need of equipping the target with a radio device. It uses the target-induced change in the received signal strength (RSS) of the wireless links to locate the target. It is useful for the applications in security monitoring and emergency rescue. However, it is difficult for the existing RSS-based DFL algorithms to acquire a high localization accuracy and a low computational complexity simultaneously. To address this issue, a novel hierarchic radio imaging (HRI)-based DFL algorithm is proposed in this article. The algorithm groups the wireless links according to the length of links and assigns a priority to each link group. Furthermore, a grid normalized model is proposed to calculate the grid values, and then a square human model is used to locate the target. In addition, in order to reduce the computational complexity, the location information of the target at the previous moment is used to limit the regional range of the target location. Extensive experiments are conducted with results showing that the HRI algorithm not only greatly reduces the computational complexity but also achieves high localization accuracy and high localization stability. Therefore, the HRI algorithm is very suitable for the real-time-based applications.